The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A catalyst may be used to change exhaust gas constituents. A catalyst does not fully convert exhaust gases until it is heated to a desired temperature. The desired temperature may be referred to as an activation temperature. Typically, an engine is started from a cold start. To reduce the amount of time to reach the activation temperature, the engine may be operated in a certain manner. Secondary air injection is one way to increase the catalyst temperature more rapidly. The increased cost and complexity of the system may be undesirable.
Another way to increase the temperature of the catalyst to the catalyst light-off temperature is to provide split-pulse injection. A split-pulse injection divides the amount of fuel to be injected into the cylinder into a primary pulse and a secondary pulse that occurs at a later time than the primary pulse. The secondary pulse may vary greatly. Regulating authorities require monitoring each injection event. The size of the secondary pulse may vary. When the secondary pulse becomes too small, detection of the secondary fuel injection event may not be achieved in a conventional manner.